Plastic is widely used for one-way applications for food wrapping materials, containers, packing materials, etc. but is actually discarded as refuse in a large quantity. Thus, in Japan, a law on recycling of wrapping and containers was recently enacted from a standpoint of reduction of quantity of refuse, saving of energy and saving of resources and obligates recycling of such plastic. In order to promote recycling of plastic, not only legal regulation but economic approach is vital. As one trial, it is proposed to lower the cost of recycled plastic through reduction of transportation and collection costs by reducing volume of plastic with a mechanical crushing and cutting machine, a mechanical compressive apparatus, a mechanical crushing and frictional heat dissolving apparatus, etc. However, these prior art apparatuses have large disposal capacities but are large and expensive and therefore, are not suitable for use in terminal collection spots such as supermarkets where a relatively small quantity of plastic is disposed of.
On the other hand, a method suitable for disposal of a relatively small quantity of plastic, in which plastic is heated at low temperatures so as to be reduced in volume, is proposed in Japanese Patent Laid-Open Publication No. 5-23655 or Japanese Patent Laid-Open Publication No. 5-92179. This method simplifies structure of the apparatuses as compared with conventional ones and is suitable for a compact apparatus for distributed disposal of a small quantity. However, in this known method, since plastic is heated so as to be reduced in volume, malodorous gas may be produced according to the kinds of plastic or heating temperature during the heating process and thus, malodor may be produced from the apparatus during and after disposal. Especially, in case where the disposal apparatus is used in stores such as supermarkets, production of malodorous gas could offer a serious problem. Furthermore, in this known method, in case plastic has been heated at an excessively high temperature due to malfunction of control of the apparatus or combustible volatiles such as kerosine are mixed into the apparatus, there is a risk in that a large quantity of combustible gas is produced and reaches its ignition point.
Therefore, in conventional disposal of waste plastic, there have been such problems that technology for removing malodor quickly and effectively should be established and ignition of produced gas should be prevented under any condition.